Embodiments of the invention relate generally to cylinder head intake port configuration for internal combustion engines and, more particularly, to intake port geometry configured to reduce fuel puddling and improve fuel atomization.
Puddling of fuel in an intake passage of an internal combustion engine leads to several undesirable conditions. Fuel puddling occurs when an engine is shut down or is run at very low speeds. In these conditions, the air stream within the intake manifold lacks sufficient velocity and turbulences to keep fuel in suspension. As a result, liquid fuel tends to settle out and collect in low areas of the intake.
When running at low speeds, liquid fuel present in the intake port may drain into the combustion chamber through the intake valve. When air stream velocity in the intake manifold increases due to acceleration, the fuel puddles are drawn into the combustion chamber and results in excess fuel present during combustion, which leads to incomplete combustion resulting in a surge of black smoke in the exhaust or backfiring through the carburetor. When fuel puddles in the intake after shut down, upon start up, the result is an overly rich air/fuel mixture that can result in misfires and audible pops.
The combustion process could be improved if the air/fuel mixture was more consistent upon start up and acceleration. A more consistent mixture will result if the evaporation rate within the intake port is increased because less liquid fuel will be present. The increased atomization will result in improved combustion and more consistent exhaust emissions.
Some engines may have modified intake port geometry to reduce fuel puddling and improve atomization. For instance, the intake port may provide for liquid fuel to drain into a high turbulent region created by a ridge or a bump. The turbulence will increase atomization of the liquid fuel and improve the air/fuel mixture. However, engines are often desired to operate in more than one orientation. Accordingly, liquid fuel may not properly drain into the turbulent region when the engine operates in a second orientation.
Therefore, it would be desirable to design a cylinder head for an internal combustion engine with an intake port to reduce fuel puddling. Also, it would be desirable to have an intake port geometry that would improve fuel atomization. It would be further advantageous if an engine could reduce fuel puddling and improve atomization when the engine is configurable for operation in different orientations.